Biomedical ultrasound (2 MHz, 1-30 W/sq.cm.) exerts demonstrable biological effects on plant systems at organismic, cytokinetic, and molecular levels. The physical basis for these effects is non-thermal, with much but not all of the biological perturbations apparently induced by acoustic cavitation. Three avenues of research are proposed, all utilizing plant root meristems (Vicia faba, Pisum sativum) known to be sensitive to ultrasound. The first deals with recovery from ultrasonically-induced damage at organismic (root growth rate), cytokinetic (cell cycle progression) and cellular macromolecular synthetic (DNA, RNA and protein) levels. The objective of this avenue is to elucidate the molecular and cellular mechanisms involved in organismic recovery from ultrasonically-induced damage. The second avenue deals with molecular damage to DNA. DNA from sonicated cells will be analyzed by density gradient analyses for single and/or double strand breakage, and DNA-protein crosslinking. The third avenue will consider cell cycle and chromosomal sensitivity to ultrasound. Cell cycle progression and cell cycle component variations (e.g., min and max S durations) will be analyzed using autoradiographic and synchronization techniques to determine if certain portions of the cell cycle are more sensitive than others to ultrasonically-induced perturbation and chromosomal aberration induction. Chromosomal aberration induction will include whether, to what degree and what form (e.g., banding variations) anomalies are induced in specific portions of the cell cycle. The significance of the proposed research is that a thorough analysis of biological responses of a system known to be sensitive to diagnostic-therapeutic ultrasound will be made. The information to be gained from this study will aid in the assessment of the potential mutagenicity and carcinogenicity of ultrasound.